All Questions
Tagged with scattering-cross-section quantum-chromodynamics
16
questions
1
vote
0
answers
60
views
Spinor-helicity formalism: relationship between 1 and 2 reference vector setups
The spinor-helicity formalism is usually set up so that for a massless vector boson (photon or gluon) with momentum $k$ an arbitrary reference momentum $p$ is introduced and the corresponding ...
- 312
1
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0
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37
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Neutron pair annihilation cross-section
I'm having a surprisingly difficult time finding this information. My expectation is that the total pair annihilation cross-section is something like $\langle\sigma v\rangle_{n\bar n}\sim \Lambda_{\rm ...
- 1,291
3
votes
1
answer
304
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Renormalization group applied to a simple QCD problem
Consider page 551 of Peskin & Schroeder's book on QFT, where he is treating the process $e^{+}e^{-} \to \text{Hadrons}$. I have 3 misunderstandings regarding some lines of thought effected there:
...
- 1,742
1
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0
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147
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Soft-gluon of scattering amplitude
The question from Scattering Amplitudes in Gauge Theory and Gravity page 46, equation (2.120) from which I can't get a consistent formula.
I just calculate A3(gff) which two fermion and one gluon $A_n\...
- 11
2
votes
0
answers
348
views
How to calculate the total cross section of a QCD process? (qq->gg)
I want to calculate the total cross section of various QCD processes (let's go with $q\bar{q}\rightarrow gg$ for this question) at tree level for some colliding hadrons at a certain energy (let's go ...
- 91
1
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0
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62
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Could the Odderon intercept be equal to $\alpha_\mathbb {O}(0)=0.813$? [closed]
The directed percolation dynamical universality class is characterized by just three independent critical exponents. These exponents are (in a 3d space):
$$\beta=\beta'=0.813(9)$$
$$\nu_\perp=0.584(5)...
- 447
1
vote
0
answers
135
views
How do soft Pomerons become hard?
The exchange of soft Pomerons (and Reggeons) ($\alpha_R(0)=0.55$ and $\alpha_P(0)=1.08$) seem to describe total hadron-hadron cross sections pretty well in the Regge limit. See, for example:
https://...
- 447
6
votes
1
answer
288
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At what stage is it necessary to introduce a field theory in the regeon-pomeron-odderon model of hadron interactions?
I've been reading some papers from G.F. Chew and S. C. Frautschi and they do not even bother to introduce the concept of "Field" when they describe hadron interactions. My impression is that they do ...
- 447
2
votes
1
answer
115
views
Do Reggeons-Pomerons-Odderons offer an Universal picture of hadron interactions?
As far as I know, the total cross-sections of the following hadron interactions are well described by a single Reggeon trajectory and a single Pomeron (soft Pomeron) trajectory. It seems to work for ...
- 447
2
votes
0
answers
78
views
Why are the elastic and total cross-section of $pp$ collisions increasing as the C.O.M. energy grows?
Well, that's about it. I don't find any reasonable explanation for this fact. Are they transversally expanding as the energy increases? Please, remember that strong interactions are short ranged and ...
- 447
2
votes
1
answer
227
views
Proton-proton and proton-antiproton elastic scattering symmetry
Is $A_{pp}(s,t)=A_{p\bar p}(t,s)$ true based on crossing symmetry?
Consider $pp$ and $p\bar p$ elastic colissions ($p + p \rightarrow p + p$ and $p + \bar p \rightarrow p + \bar p$). The scattering ...
- 447
1
vote
1
answer
298
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Proton-proton collisions cross section plot by Stirling
I am struggling to understand some details of the cross section plot by Stirling that is very often shown when talking about LHC physics. See e.g. here: http://www.hep.ph.ic.ac.uk/~wstirlin/plots/...
- 11
1
vote
0
answers
140
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Deep inelastic scattering and the $Q^2 \rightarrow \infty$ limit.
I am reading through Bailin and Love's argument (see P.151-152 of 'Introduction to Gauge Field Theory') that as $Q^2 \rightarrow \infty$, we probe the product of the two electromagnetic currents ...
- 3,569
4
votes
1
answer
1k
views
Callan-Gross relation validity
The inelastic electron-proton scattering cross section can be written as
$$\frac{d\sigma}{dE_2d\Omega}=\frac{\alpha^2}{4*E_1\sin^4{\frac{\theta}{2}}}(W_2\cos^2{{\frac{\theta}{2}}}+2W_1\sin^2{{\frac{\...
- 263
7
votes
1
answer
3k
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How to sum over final, and average over initial color states?
Consider the $s$-channel mediated top quark production process
$$ d + \overline d \rightarrow t + \overline t$$
Using the Feynman rules for QCD, the amplitude contains a color factor
$$[c^\dagger _{\...
